ADCC activity against RPMI 8226 cells by normal human PBMCs. (A) ⁵¹Cr-labeled RPMI 8226 cells were incubated with PBMCs at an E/T ratio of 50 along with various concentrations of antibodies. (B) ⁵¹Cr-labeled RPMI 8226 cells were incubated with PBMCs in the presence of 1 μg/mL of antibodies. Symbols represent control human IgG (○), mouse anti-HM1.24 MoAb (▵), chimeric anti-HM1.24 MoAb (▪) and humanized anti-HM1.24 MoAb (•). Data represent the mean ± SD of triplicates.